Materials & grades
ASTM A193 Grade B16 chromium-molybdenum-vanadium bolting steel (40CrMoV4-6, SNB16)
ASTM A193 Grade B16 is a chromium-molybdenum-vanadium bolting steel for higher temperatures than B7. Its European counterpart is 40CrMoV4-6 (1.7711) and its Japanese counterpart is SNB16.
Names by standard
What it is called in each region
| Region | System | Designation | Standard | Match |
|---|---|---|---|---|
| USA | ASTM A193/A193M | Grade B16Cr-Mo-V alloy bolting, quenched and tempered at 1200 °F (650 °C) minimum. No AISI/SAE number applies. | ASTM A193/A193M | Same material |
| UK | BS EN 10269 | 40CrMoV4-6BSI adopts EN 10269. Composition and properties are close to B16 but not identical. | BS EN 10269 | Closest equivalent |
| EU | EN 10027-1 name | 40CrMoV4-6Mill datasheets list A193 B16 as the similar designation. EN 10269 also sets minimum Rp0.2 at elevated temperature. | EN 10269 | Closest equivalent |
| EN 10027-2 number | 1.7711 | EN 10269 | Closest equivalent | |
| DIN (superseded) | 40CrMoV4-7Older German name for the same steel, still printed on charts. Some references quote 40CrMoV4-7 for the EN grade. | — | Closest equivalent | |
| EN 10027-1 name | 21CrMoV5-7 (1.7709)Another vanadium-alloyed bolting steel in EN 10269, with more chromium (1.20–1.50%) and less carbon (0.17–0.25%). Not a B16 match. | EN 10269 | Closest equivalent | |
| Japan | JIS G 4107 | SNB16JIS high-temperature bolting steel with chromium, molybdenum and vanadium. Carbon limit (0.36–0.44%) is lower than B16 (0.36–0.47%). | JIS G 4107 | Closest equivalent |
On equivalence
- B16 is an ordering specification, not a steel grade. The steel is a Cr-Mo-V alloy. 40CrMoV4-6 (1.7711) is the standard European counterpart. Mill datasheets list A193 B16 as the similar designation.
- Composition differs between the two. B16 allows 0.36–0.47% carbon and 0.45–0.70% manganese; 40CrMoV4-6 in EN 10269 allows 0.36–0.44% carbon and 0.45–0.85% manganese, with 0.90–1.20% chromium. The mill specification narrows the grade further.
- 21CrMoV5-7 (1.7709) is another EN 10269 bolting steel with vanadium, but it has 0.17–0.25% carbon and 1.20–1.50% chromium. Treat it as a separate steel, not a B16 substitute.
- Japan: SNB16 (JIS G 4107) is the counterpart. The composition data we could read is partial, and a data page lists minimum tensile and yield values for SNB16 of 690 and 590 MPa, apparently for the larger size band. Check the standard before substituting.
- India: we did not find a verified IS designation for B16. Indian specifications order it as ASTM A193 B16.
- B16 is not interchangeable with B7 for temperature or nut selection. A193 B7 requires 2H nuts; B16 requires grade 7 (or 4) nuts.
Chemical composition
Composition limits, mass %
| Element | B16USA · ASTM A193/A193M, Grade B16 (heat analysis) | 40CrMoV4-6 (1.7711)EU · EN 10269 (cast analysis) | 40CrMoV4-6EU · Ovako mill specification, variant 6098 (cast analysis) | SNB16Japan · JIS G 4107 (partial, as listed by Total Materia) |
|---|---|---|---|---|
| C | 0.36–0.47 | 0.36–0.44 | 0.36–0.44 | 0.36–0.44 |
| Si | 0.15–0.35 | ≤0.40 | 0.15–0.35 | — |
| Mn | 0.45–0.70 | 0.45–0.85 | 0.45–0.70 | 0.45–0.70 |
| P | ≤0.035 | ≤0.025 | ≤0.025 | — |
| S | ≤0.040 | ≤0.030 | ≤0.025 | — |
| Cr | 0.80–1.15 | 0.90–1.20 | 0.80–1.15 | 0.80–1.15 |
| Mo | 0.50–0.65 | 0.50–0.65 | 0.50–0.65 | — |
| V | 0.25–0.35 | 0.25–0.35 | 0.25–0.35 | — |
| Al | ≤0.015 | ≤0.015 | ≤0.020 | — |
Mechanical properties
Strength and hardness
| Condition | Tensile strength | Yield strength | Elongation | Hardness |
|---|---|---|---|---|
| Quenched and tempered, minimum tempering temperature 1200 °F (650 °C)Specified minimums, diameter up to 2½ in (up to M64). Elongation 18%, reduction of area 50%. Hardness 321 HBW or 35 HRC maximum.ASTM A193/A193M Grade B16, via Torqbolt | ≥860 MPa≥125 ksi | ≥725 MPa≥105 ksi | ≥18 % | ≤321 HBW / ≤35 HRC |
| Quenched and tempered, minimum tempering temperature 1200 °F (650 °C)Specified minimums, diameter over 2½ to 4 in (over M64 to M100). Elongation 17%, reduction of area 45%.ASTM A193/A193M Grade B16, via Torqbolt | ≥760 MPa≥110 ksi | ≥655 MPa≥95 ksi | ≥17 % | ≤321 HBW / ≤35 HRC |
| Quenched and tempered, minimum tempering temperature 1200 °F (650 °C)Specified minimums, diameter over 4 to 8 in (over M100 to M200). Elongation 16%, reduction of area 45%.ASTM A193/A193M Grade B16, via Torqbolt | ≥690 MPa≥100 ksi | ≥585 MPa≥85 ksi | ≥16 % | ≤321 HBW / ≤35 HRC |
| EN 10269 40CrMoV4-6, quenched and tempered (+QT)Specified, diameter up to 100 mm; yield and elongation are minimums. Reduction of area at least 45%. Comparison only; not an A193 value.EN 10269, 40CrMoV4-6, via Torqbolt | 850–1000 MPa123–145 ksi | ≥700 MPa≥102 ksi | ≥14 % | — |
| EN 10269 40CrMoV4-6, quenched and tempered (+QT)Specified, diameter over 100 to 150 mm; yield and elongation are minimums. Reduction of area at least 45%. Comparison only.EN 10269, 40CrMoV4-6, via Torqbolt | 850–1000 MPa123–145 ksi | ≥640 MPa≥93 ksi | ≥14 % | — |
| Ovako 40CrMoV4-6 (variant 6098), quenched and tempered (+QT)Mill specification, round bar over 25 to 65 mm. Reduction of area at least 50%. Hardness 250–300 HB.Ovako 40CrMoV4-6 material data sheet | 860–1000 MPa125–145 ksi | ≥725 MPa≥105 ksi | ≥14 % | 250–300 HB |
In practice
Behaviour, heat treatment and uses
Characteristics
- B16 adds about 0.25–0.35% vanadium and about three times the molybdenum of B7 (0.50–0.65% against 0.15–0.25%). One supplier source credits the vanadium and the higher tempering temperature for better load retention at temperature.
- B16 is tempered at 1200 °F (650 °C) minimum, 100 °F above B7. The higher tempering temperature leaves it more stable in service at temperatures where B7 would creep.
- Room-temperature strength is the same as B7 up to 2½ in (125 ksi tensile, 105 ksi yield), but elongation is higher at 18% and the specification covers bars up to 8 in, rather than 7 in.
- Fastener sources describe B16 for temperatures above where B7 is used. One gives about 750–1100 °F; another gives about 900 °F (480 °C) as its limit. The sources disagree, so take the allowable stress and temperature limit from the design code.
- B16 is paired with A194 Grade 16, the chromium-molybdenum-vanadium nut grade made for it, or with Grade 7 (Grade 4 in older practice). A 2H nut relaxes faster than the stud at temperature and becomes the weak point.
- Optional A193 supplementary requirements include a narrower hardness band (253–319 HBW) for bolts up to 2½ in and a stress-rupture test at 1100 °F and 20 ksi for at least 25 hours.
- B16 costs more than B7 (one source puts it at 10–20% more) because of the vanadium and molybdenum.
Heat treatment
- Bar is hot-wrought, quenched and tempered at 1200 °F (650 °C) or higher. A tempering temperature at or above 650 °C is also quoted for JIS SNB16.
- Stress relieving, when ordered through the supplementary requirement, is done at 100 °F (55 °C) below the tempering temperature.
- Mill transformation points for 40CrMoV4-6: Ac1 about 739 °C, Ac3 about 804 °C, Ms about 323 °C (Ovako data).
Impieghi tipici
- Studs and bolts in high-temperature flanged joints in power and process plant
- Joints where B7 would relax and leak at service temperature
- Paired with A194 Grade 16 or Grade 7 nuts
Bolting steels
Similar grades compared
| Classe | C % | Mn % | Cr % | Ni % | Tensile, first listed condition |
|---|---|---|---|---|---|
| A193 B16 | 0.36–0.47 | 0.45–0.70 | 0.80–1.15 | — | ≥860 MPa |
| A193 B7 | 0.37–0.49 | 0.65–1.10 | 0.75–1.20 | — | ≥860 MPa |
| A320 L7 | 0.38–0.48 | 0.75–1.00 | 0.80–1.10 | — | ≥860 MPa |
| A193 B8 / B8M | ≤0.08 | ≤2.00 | 18.0–20.0 | 8.0–11.0 | ≥515 MPa |
| A194 2H | ≥0.40 | ≤1.00 | 0.80–1.10 | ≤0.40 | 500–650 MPa |
Composition from the US standard where one exists, otherwise the first standard listed on each grade's page. Strength conditions differ between grades; open a grade for its full table.
Domande e risposte
Common questions
What is the equivalent of A193 B16?
The nearest European steel is 40CrMoV4-6 (1.7711) in EN 10269, and the nearest Japanese grade is SNB16 in JIS G 4107. They are close, not identical: the carbon, manganese and chromium limits differ. We found no verified Indian designation, so B16 is ordered by its ASTM name.
What is the difference between A193 B7 and B16?
B16 is a chromium-molybdenum-vanadium steel tempered at 1200 °F (650 °C) minimum, against 1100 °F (593 °C) for B7. Both reach 125 ksi tensile up to 2½ in, but B16 resists relaxation better at high temperature. B7 takes 2H nuts and B16 takes Grade 16 or Grade 7 nuts.
What nut do I use with A193 B16?
A194 Grade 16, the chromium-molybdenum-vanadium nut grade made for B16, or Grade 7 (Grade 4 in older practice). Using Grade 2H nuts on high-temperature B16 joints makes the nut the weak link, because 2H relaxes more than the stud.
What temperature can A193 B16 be used at?
Fastener sources put the upper range from about 900 °F (480 °C) to 1100 °F (590 °C), so they disagree. The grade's own specification does not set a temperature limit. The allowable stress at temperature comes from the design code, such as ASME Section II Part D.
From the Corona catalog
Products listed with A193 B16
Keep reading
Related references
References
Sources
- ASTM International, A193/A193M scope and abstract (alloy-steel and stainless steel bolting for high temperature or high pressure service) — Scope, grade families, nuts and A320 cross-reference; the full tables are paywalled.
- Torqbolt, ASTM A193/A193M grades B7, B7M, B16, B8, B8M — Composition, strength by diameter band, minimum tempering temperature and supplementary requirements, transcribed from A193.
- Ovako Steel Navigator, 40CrMoV4-6 material data sheet — Lists ASTM A193 B16 as a similar designation; mill composition and +QT properties.
- Standards.ie (NSAI shop), EN 10269:2013 Steels and nickel alloys for fasteners with specified elevated and/or low temperature properties — Title, scope and status of the CEN standard.
- Torqbolt, EN 10269 bolting steels overview — Grades covered by EN 10269 and the compositions and properties of X5CrNi18-10, X5CrNiMo17-12-2, C35E and 21CrMoV5-7.
- Hex Technology, The Stud Guide: B7s, B16s and other common bolt materials — Typical service ranges, nut pairings and grade-selection notes from a fastener maker.
- Projectmaterials, A193 B7 vs B16 — B7 and B16 comparison, relaxation and nut pairing.
- Total Materia, JIS SNB 16 (G 4107) — Partial SNB16 composition, minimum tempering temperature and cross-references (EN 40CrMoV4-6).
- Aichi Steel, alloy steel bolting materials for high temperature service — Confirms JIS G 4107 as the standard for SNB7 to SNB16 bolting steels.
- ASTM A193/A193M-10a, hosted copy of the full standard — B16 composition, strength by diameter (inch and metric), 1200 °F tempering, 1700–1750 °F oil quench, S4 hardness band, S12 stress rupture. 2010 edition, read by the independent checker.
- Ovako Steel Navigator, 40CrMoV4-6 material data sheet — Variant 6098 composition, +QT properties and transformation temperatures; lists A193 B16 as the similar designation.
Values summarize published limits and typical data. The governing standard and the current edition control; check them before specifying.